Method of assembling a heat exchanger



April 28, 1970 F, A BUR NE 5-. AL 3,508,312

METHOD OF ASSEMBLING A HEAT EXCHANGER Flled Jan. 15, 1968 4 Sheets-Sheet1 INVENTORS FRE DER/CK A. BUR/V5 E ME I?! VALY/ H6 '78 BY M ATTORNEY F.A. BURNE E A 3,508,312

METHOD OF ASSEMBLING A HEAT EXCHANGER 1968 4 Sheets-Sheet 2 INVENTOR s:FREDERICK A. BURNE ATTORNEY A ri128, 1970 Flled Jam. 15,

April 28, 1970 F. A. BURNE ET AL 3,508,312 v METHOD OF ASSEMBLING A HEATEXCHANGER 4 Sheets-Sheet 3 FIG 1175A [[76 MB INVENTORS. FREDERICK A.BU/PNE EMER) l VALY/ ATTORNEY April 28, 1970 A. BURNE ET 8,

METEOD O F ASSEMBLING A HEAT EXCHANGER Filed Jan. 15 1968 INVENTORS.FREDER/CK A. BUR/V5 4 Sheets-Sheet 4.

EME/PY VALYI' ATTORNEY United States Patent US. Cl. 29157.3 15 ClaimsABSTRACT OF THE DISCLOSURE A method of assembling a heat exchanger froma plurality of modular units, the units comprising at least one tubeconductively bonded to a layer of pervious material. The contour ofthese units is such that they can be fitted together and assembled toform heat exchangers of any desired size and length which avoidsubstantial by-pass.

This invention relates to heat exchangers and in particular relates tomodular heat exchange units and the use thereof comprising tubesconductively bonded to a layer of pervious material, the layer ofpervious material being so contoured as to engage other such members toform heat enchangers of any desired size and length.

FIGURE 1 is a schematic sectional view of a heat exchanger according tothe prior art.

FIGURE 2 is a sectional view of the modular units according to thepresent invention.

FIGURE 3 is a sectional view of the modular units shown in FIGURE 2assembled into a heat exchanger.

FIGURE 3a is a sectional view illustrating the modular units with atangential design of the tubes in the units.

FIGURE 4 is a sectional view of the modular units according to thepresent invention with the tubes having an elliptical cross section.

FIGURE 5 is a sectional view of a modular unit according to the presentinvention in which the contour of the modular. unit is designed to fitadjacent a shell when the heat exchanger is assembled.

FIGURE 6 is a sectional view of a modular unit according to the presentinvention designed to fit adjacent a shell wherein the tubes have anelliptical cross section.

FIGURE 7a is a sectional view of a modular unit according to the presentinvention provided with fins in the layer of porous material.

FIGURE 7b is a sectional view along the lines 7b of FIGURE 7a.

FIGURE 8 is a sectional view of modular units according to the presentinvention having a cooperating contour.

FIGURE 9a is a sectional view of modular units according to the presentinvention showing another cooperating contour.

FIGURE 9b is a sectional view of modular units according to the presentinvention showing still another cooperating contour.

I FIGURE 10 is asectional view of the modular units according to thepresent invention wherein sealing strips are provided between the unitsto reduce by-pass.

FIGURE 11 is a sectional view of a unit according to the presentinvention provided with side plates to reduce by-pass.

FIGURE 12 is a sectional view of the modular units according to thepresent invention provided with inserts to reduce by-pass.

FIGURE 13 is a sectional view along the lines 13-13 in FIGURE 12.

FIGURE 14 is a sectional view of the modular units "ice according to thepresent invention illustrating one geometric arrangement of the units.

FIGURE 15 is a sectional view of a modular unit accorded to the presentinvention illustrating an improved geometric arrangement.

FIGURES 15a and 15b are sectional views of the modular unitsillustrating another geometricarrangement of the units.

FIGURE 16 is a sectional view of the modular units according to thepresent invention illustrating a favorable geometric arrangement ofunits together with the use of sealing strips between the units.

FIGURE 17 is a sectional view of a modular unit of the present inventionhaving an extended tube portion for engagement with header plates.

FIGURE 18 is a sectional view of a heat exchanger in which the modularunits according to FIGURE 17 are assembled in header plates.

FIGURE 19 is a partial sectional view of the modular units of thepresent invention provided with a drawn cup.

FIGURE 20 is a sectional view of a multi-tube unit according to thepresent invention.

FIGURE 21 is a top view of the multi-tube unit in FIGURE 20.

FIGURE 22 is a sectional view of a heat exchanger in which themulti-tube units of the present invention are shown in variousembodiments.

It is an object of this invention to provide a heat exchanger made up ofunits comprising tubes conductively bonded to a layer of porousmaterial.

It is another object of this invention to provide heat exchange unitswhich can be used in either large or small heat exchangers.

It is another object of this invention to provide heat exchange unitscomprising tubes conductively bonded to a layer of porous material, thesize of the units being such that uniform brazing can be obtainedthroughout the entire layer of porous material in the units.

It is another object of the present invention to provide a method ofexchanging heat in which one fluid is to pass through tubes and anotherheat exchange medium is to pass through a porous material conductivelybonded to the tubes and in which there is no substantial by-pass of theheat exchange fluid which is to pass through the porous material.

It is another object of this invention to provide heat exchange unitswhich can be brazed without the use of an unduly large furnace.

It is another object of the present invention to control the path of theheat exchange fluid passing through the porous material to minimizeby-pass.

It is another object of the present invention to provide a heat exchangecore made up of the heat exchange units of the present invention.

Other objects will appear from the following description and drawings.

'In US. Patent 3,289,750, assigned to the assignee of the presentapplication, heat exchange structures are described consisting of aheat-conductively bonded composite of solid and pervious metal, whereinthe heating or cooling fluid is separated from the substance to beheated or cooled by an impervious barrier. Such structures have beenshown to be very effective in heat transfer applications.

FIGURE 1 shows schematically one of such heat exchangers, verysuccessfully produced in which a shell 1 contains a core 2 consisting ofpermeable metal containing tubes 3 embedded therein. Such heatexchangers are very eflicient when designed within certain knowndimensional limits.

Such heat exchangers are usually made by first preparing a solid metalassembly and filling it with particulate metal of a desired size,together with a still finer brazing metal or alloy. A brazing operationfollows which joins the entire structure together. In general, theresulting brazed structure contains metal particles, for example,sphericaly shaped, joined by brazing. It is desired to have relativelylarge brazed joints to provide for good heat conduction between themetal particles. This can only be obtained if the time at brazingtemperature is not long (for example, for a phosphorus containing copperbrazing alloy, less than minutes at 1-6 00 F Long times (e.g., more thanminutes at 1600 F. for this brazing alloy) result in diffusion of thebrazing alloy into the particulate metal particles and a correspondingreduction in the size of the remaining joint area. The particulartemperatures and times vary with the particular brazing alloy, but theprinciple is the same. The reduced area of the brazed joints results inlower heat conductance through them between adjoining metal particles.

The designs and schemes disclosed to date are limited to structuresincluding an entire unit, or a core which needs only to have the shelladded for completion. The entire unit or the core must usually be smallbecause, in the course of brazing, the centeras well as the surface ofthe porous layer must reach brazing temperature, all within less timethen it takes for harmful loss of brazing material to occur, lest undoloss of heat conductance from one metal particle to the other results.

Size of such a one-piece unit is also limited by the brazing furnace.Considerations including atmosphere penetration, heat penetration andtotal heat requirement limit the size. One of the three lineardimensions of the onepiece units should not exceed 3 to 4 inches as apractical value. Beyond this, the atmosphere does not penetrate. Weightper piece should not be too great because an excessively long time toheat to brazing temperature would be required or an excessively largefurnace would be required. As mentioned previously, if the weight ordimensions of the unit are excessive, the time in the furnace is suchthat the exterior of the unit is at brazing temperature for too long atime while the interior or center is rising to brazing temperature. Thisreduces the cross sectional area of the brazed bond near the surface andthus causes a reduction in heat conduction at that location.

The present concept solves the inherent problems encountered inattempting to apply one-piece units to applications in large heatexchangers.

According to the present invention, units 4 are produced containingtubes 3 of desired lengths conductively bonded to a layer of porousmaterial 2, as shown in FIGURE 2. Such elements 4 can be readilymanufactured in practically unlimited length. F or a single unit, theporous layer 2 which is perpendicular to the direction of flow of thefluid passing through the porous material (vertically downward in FIGURE3) is designed to effect an acceptable compromise of good heat transferand low pressure drop. While the thickness of the porous layer will varyfrom one application to another, a thickness of 0.05 to 0.1 inch hasbeen found effective in many instances.

The units thus formed may then be mechanically assembled in apredetermined pattern and put into a heat exchanger of any size, such asthe one shown schematicaly in FIGURE 3. The result would thus begeometrically similar to the structure of FIGURE 1.

Thus, in the exemplary embodiment of the present invention in FIGURE 3,one fluid will'enter through conduit 5, pass into the void space "6, andwill then penetrate and flow through the porous material 2 as it passesdownwardly through the plurality of assembled units 4. While this fluidis in contact with the porous material 2, a second fluid, passingthrough the tubes 3, will be in heat exchange relation with the firstfluid throughout the porous material. The first heat exchange mediumwill then be collected in the void space 7 and pass out at 8.

It is seen that with this arrangement intimate contact is obtainedbetween the first heat exchange medium which enters at '5 and the porousmaterial 2 and that substantially all of the first heat exchange fluidis in heat exchange relation with the pervious material 4.

To function well, substantial flow of fluid outside the porous materialmust be avoided in the assembled units. Thus, by-pass may occur betweenthese units at a resistance to flow which is less than the one withinthe porous layer. Then, a substantial portion of the fluid willparticipate in heat exchange to a greatly reduced extent. Provisiontherefore must be made to assure that substantially all of the heatexchange fluid which enters the shell 1 will be in heat exchangerelation with porous material 2 by virtue of being forced to flowthrough that material.

These modules, either single or multiple tubes, can be made in long,continuous lengths of standard sizes. Lengths of up to 20 feet may beproduced if desired. The tubes with the porous extended surface may thenbe used in making either large or small heat exchangers, in a similarmanner to that in which bare tube or finned tubing is presently used. I

The heat exchange units 4 can be made in practically any desired lengthbecause the thickness of the porous layer is such that it will fit intoexisting furnaces and can be eifectively brazed therein. It is notdifficult to braze effectively at the center, as well as at the edge ofthe porous material.

Thus, it is seen that formation of the tubes 3 and porous layer 2through the use of the modular units 4 has considerable advantage fromthe standpoint of flexibility of size of heat exchangers which can beproduced over the construction shown in FIGURE 1, which is limited to asize, as before explained. i

It can be seen from FIGURE 3 that there is a space 9 between the tubes 3filled with porouts material 2. The heat exchange medium which ispassing vertically downward through the porous material will not passthrough the space 9 except to a very limited extent, and little heatwill be exchanged therein. Thus, this space 9 constitutes ineflicientuse of the porous material 2. Thus, an improved unit is shown in FIGURE3a in which the tubes 3a extend to the surface of the units. It isapparent that, in an assembly, this design of the units avoids theineificient space 9 shown in FIGURE 3.

The tubes may have any desired cross section. For instance, the units 14shown in FIGURE 4 contain tubes '13 having elliptical cross sectionswithin the pervious material 12.

To avoid by-pass, the units which are to be placed against the shellwall 1 are preferably contoured. Thus, in FIGURE 5, in the unit 34having circular tubes 33, the porous material is contoured at 35 to fitagainst a shell such as '1 in FIGURE 3. Likewise, the unit 44 in FIG-URE 6 having elliptical tubes 43 is contoured at 45 to fit against sucha shell. FIGURE 6 also shows the tangential design of the units 44, withthe elliptical tubes 43 extending to the surface of the unit 44.

In another embodiment of the invention shown in FIG- URES 7a and 7b, theunits 444 have tubes 443. Bonded to the tubes 443 is pervious material442. However, the tubes 443 also have fin members 445. These fin members445 are conductively bonded to the pervious material 442 and to thetubes 443. The fins 445 may be placed below the surface of the porousmaterial, or they may extend to the surface or above the surface, asdesired. This embodiment is more efficient in heat transfer due to thecombined effects of the porous material 442 and the fins 445.

In making the mechanical joint between units, it is often difficult toavoid a small amount of by-pass between abutting surfaces or adjoiningelements. In whatever joint such by-pass became readily possible, theheat exchange medium would preferably pass through it, rather thanthrough the porous body itself because this joint would offer lessresistance to flow.

Thus, for an even more efficient heat exchange, it is desirable toprovide structures which minimize and/or eliminate such by-pass.

One method of reducing by-pass is the provision of contours on the unitswhich fit together and interlock. Thus, as shown in FIGURE 8, the units54 comprising tubes 53 and pervious material 52 have a cooperatingcontour as shown at 55.

In the embodiment shown in FIGURE 9a, the units 64 comprising tubes 63and pervious material 62, have interlocking contours shown at 68 and 69.These two contours cooperate to reduce by-pass.

Still another exemplary embodiment is shown in FIG- URE 9b in which theunits 74, including tubes 73 and pervious material sections 72, haveinterlocking S shaped contours 75 and 76.

It will be understood that the preceding geometric arrangements may bevaried according to manufacturing considerations which providecross-sections which are easy to fabricate and still satisfy the need ofreducing by-pass.

Another method of eliminating or reducing by-pass and thereby insuringthat essentially all of the heat exchange fluid flows through the porousmatrix is the use of sealants, examples of which include plastic tape,shaped extrusions, mastic tape, rubber sheets, cements, side plates,etc., between adjacent modular surfaces.

Thus, in another embodiment of the invention, each element may beprovided with a sealing layer at all places along which by-pass is to beprevented. Such a sealing layer may consist of thin gage soft metal or,if temperatures at which the heat exchanger is to be used permit,preferably of a plastic film, either of which may be provided with acontact adhesive layer for easier application. Thus, a roll of thesealing material may be provided in the manner of a conventionaladhesive strip roll. The requisite amount of sealing strip may then beattached to the element immediately prior to assembly. Alternately, theelements may be so equipped in the course of manufacture, therebyassuring that the right orientation in assembly is observed.

In the embodiment shown in FIGURE 10, the units 94 having tubes 93 andpervious material 92, are separated by sealing strips 96. These strips,for example, may be attached to units 94 by means of an adhesive such asglue or paste or the like. The sealing strips 96 may, for example, bemade of plastic.

Alternately, if a higher temperature operational unit is to be used, asshown in FIGURE 11, the units 104 having pervious material 102conductively bonded to the tubes 103 may have metallic side plates 105attached to the pervious material 102. These metallic side plates, forexample, may be brazed to the pervious material 102.

In the embodiments of the invention shown in FIG- URES 12 and 13, thetubes 81 are embedded in porous material 83 and so bonded as to provideheat transfer and conductance from one to the other. A series of suchtubes are then placed in tube headers 87 and sealed conventionally at88. Inserts made of plastic or metal 84 and 85 are placed between thetubes 81, thus forcing fluid flow in direction of arrow 89 to flow asindicated by arrows 89a. The second fluid flows inside the tubes indirection of arrow 80.

Flow of the two fluids in this structure may be arranged so as to beparallel, in series, or in series and parallel, depending on thedesigners choice.

Open inserts 84 having void space 86, or closed inserts 85 may be used.Seals 85a similar to 84 and 85 may be used between end tubes 81a and theinner shell wall W.

The porous layer may surround the tubes fully or partially, so long asthe inserts are formed to provide flow through the entire porous layer.

In FIGURE 14 four units 114 are shown having tubes 113 and perviousmaterial 112. The portions 112a of the pervious material next to thetubes are in very effective heat exchange relationship with the tubes,while portions 112]) are in less effective heat exchange relation,because the effectiveness of the porous material at any point isinversely proportional to its distance from the tubes 113. Moreover, inthe pattern shown, there is an opportunity for fluid flowing in thedirection of the arrows to by-pass the pervious material 112 between theunits 114 along the abutting line 115 In order to avoid these drawbacksof the arrangement of FIGURE 14, the geometric arrangement shown inFIGURE 15 may be preferred in which the units 124 are staggered, as forexample when the edges of units 124 are in line with tubes 123, with thepath of heat exchange medium through the pervious material 122 shown bythe arrows 126. It is apparent that, in this embodiment of theinvention, the opportunity for fluid to by-pass between the units isreduced, by forcing the fluid through a tortuous abutting path. Insteadof following the sharp curve 128, the heat exchange medium passingthrough the abutting void 127 will pass into the porous medium 122 inheat exchange relation with tubes 123.

Additionally, for even more efficient heat exchange, the embodimentshown in FIGURES 15a and 15b may be utilized. Thus, in FIGURE 15a, theunits 124a made of porous material 122a conductively bonded to tubes123a are nested by their cooperating contours 125a and 126a. It isapparent that-with this nesting arrangement, the distance between theinterface of the units and the tubes 123a is less than in the case ofeither FIGURE 14 or 15. Since heat exchange is inversely proportional tothe distance from any point in the porous media to the tubes, it isapparent that arrangement is more efficient than that shown in eitherFIGURE 14 or 15.

This nesting arrangement also provides the advantage of FIGURE 15 inthat a heat exchange medium passing through the abutting void 127a mustagain follow a tortuous curve 128a or 129a in order to remain in theabutting void. Rather than do this, the heat exchange medium willpreferably pass through the porous layer 122a and thus be in heatexchange relation therein with the tubes 123a.

The embodiment shown in FIGURE 15b is basically the same as that shownin FIGURE 15 except that the contours 125b and 126b are shapeddifferently. As was the case in FIGURE 15a, the distance from theinterface to the tubes 123b is less in this embodiment than in theembodiments shown in FIGURES 14 and 15, except for possibly at thecooperating points 130. Furthermore, a heat exchange medium passingthrough the abutting void 1271; will preferably pass into the porouslayer 122b in preference to the tortuous abutting void paths 12812 and12%.

Thus, the embodiments shown in FIGURES 15a and 15b provide the advantageof both staggering and nesting.

The staggered arrangement may be combined with the previously describedembodiment directed to the use of inserts or sealing strips between theunits. Thus, in the embodiment shown in FIGURE 16, the units 134comprising tubes 133 conductively bonded to pervious material 132. Theseunits 134 are separated by sealing strips 135. Furthermore, the rows 136of the units 134 spaced apart by inserts are in a staggered relationshipwith the center of the sealing strip 135 of one row being in line withthe center of the tube 133 of the row above it. Thus, by-pass is held toa particularly low level in this embodiment since both the sealingstrips and the staggered configuration act to reduce by-pass.

As shown in FIGURE 17, the units 154 may have tubes 153 with an extendedportion 155 beyond the pervious material 152 adapted to engage headerplates or end plates.

Thus, in FIGURE 18, which is a sectional view of an exemplary heatexchanger, the extended portions 155 may engage the plates 156 and 157at 155a and may extend beyond the plates, as shown at 15512.

A fluid to be heated or cooled may enter through conduit 150 and passinto void space 151. It then passes through the pervious materialportion 152 which surrounds the tubes 153 in the units 154. A secondheat exchange fluid enters void space 158 from conduit 159. The secondheat exchange fluid will pass through tubes 1'53 and exchange heat withthe first heat exchange medium before passing into void space 160 andout into conduit 161. The first heat exchange medium will then pass intovoid space 162 and pass out through conduit 163.

As shown in FIGURE 19, the units 174 may include a drawn cup 176 havinga flange 177 adapted to engage a header plate 178 or another drawn cupbelong to an adjacent unit 179. Again, extended portion 175 of tubes 173is shown beyond pervious material 172.

In FIGURES 20 and 21, a multi-tube unit 204 is shown comprising two ormore tubes 203 retained in spaced relationship by pervious material 202.These units 204 can be designed to conform to specific shapes. Forexample, they may conform to a tubular heat exchanger Shell 205 due toappropriate shape of the edge portions of the units 206. If desired, theunits 204 may be provided with extender portions 207 for header plateengagement as shown in FIGURE 21. Several units of this kind may then bearranged in an assembly generally in keeping with the before describedembodiments. There is less tendency for by-pass in these assembliesinasmuch as there is a reduced number of gaps corresponding to eachtube.

A variety of multi-tube units may be combined in a single assembly, asshown at 210, 211, 212, 213 and 214, some appropriately contoured to bein conformity with the shell 205. Such multi-tube units have the addedadvantage over single tube units of reducing the labor of assembly.Installations may be also designed to encompass a plurality of eithersingle tube units 216 or multi-tube units 217, all within a given row.If desired, sealing members may be utilized between the units, asillustrated at 215. Some of the tubes such as tubes 203 in unit 212 mayextend to the surface of the multi-tube unit.

It is to be understood that the invention is not limited to theillustrations described and shown herein, which are deemed to be merelyillustrative of the best modes of carrying out the invention, and whichare susceptible of modifications of form, size, arrangement of parts anddetail of operation. The invention is intended to encompass all suchmodifications which are within its spirit and scope, as set forth in theappended claims.

What is claimed is:

1. A method of assembling a heat exchanger comprising providing a hollowshell, placing within said shell a plurality of modular units, each saidunits comprising at least one tube conductively bonded to a layer ofporous material, the external surfaces of the porous layers beingcontoured to cooperate with and about the porous layer on adjacent unitsor, respectively, the inner surface of said hollow shell, placing saidunits within the hollow shell so that the external surfaces of the saidporous layers cooperate and are in abutment with each other and theexternal surfaces of these units which are adjacent the inner surface ofsaid shell, cooperating with the inner surface of said shell, so thatwhen a first heat exchange medium is passed through said hollow shell,substantially all of said first heat exchange medium will be in heatexchange relation with a second heat exchange medium passing throughsaid tubes.

2. A process according to claim 1 in which sealing means are placedbetween adjacent units to avoid by-pass.

3. A process according to claim 1 in which the units are assembled in astaggered relationship to avoid by-pass.

4. A process according to claim 3 in which said staggered units arenested.

5. A process according to claim 2 in which the units are assembled in astaggered relationship to avoid by-pass.

6. A process according to claim 1 in which said units are fitted intoheaders through which said second heat exchange medium passes.

7. A process according to claim 1 in which at least one of said unitscontains more than one tube.

8. A process according to claim 7 in which said multitube unit alsocontains at least one insert to avoid by-pass.

9. A process according to claim 7 in which said units are arranged in astaggered relationship.

10. A process according to claim 8 in which said units are arranged in astaggered relationship.

11. A process according to claim 1 in which inserts are provided betweensaid shell and said layer of porous material.

- 12. A process according to claim 1 in which a portion of the outersurface of said tubes contacts the external surface of said units.

13-. A process according to claim 1 in which the tubes are ellipticallyshaped in cross section.

14. A process according to claim 1 in which the tubes are circular incross section.

15. A process according to claim 2 in which said sealing means areselected from the group consisting of metallic side plates, shapedextrusions, mastic tapes, rubber sheets and cement.

References Cited UNITED STATES PATENTS 1,670,127 5/ 1928 Stancliffe -1652,401,797 6/ 1946 Rasmussen 165-180 X 2,974,404 3/1961 Humenik et al.29-1573 3,262,190 7/ 1966 Rostoker et al. 29-1573 3,306,353 2/1967 Burne165-180 X JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, AssistantExaminer U.S. Cl. X.R. 29-469 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3,503,312 Dated April 28, 1970 Inventor) FrederickA. Burma and Emery I. Valyi It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

In column 1, line 26, cancel "enchangers" and insert exchangers--. Incolumn 3, line 6, cancel "sphericaly" and insert --spherically-; incolumn 3, line 9, insert --toofollowing "not". In column 4, line 36,cancel "porouts" and insert --porous--; in column 4, line 73, cancel"or" and insert -of--. In column 6, line 45, insert -a-- following '15".In column 7, line 15, cancel "belong" and insert -belonging--; in column7, line 57, cancel "about" and insert --abut--. In column 8, line 4,cancel "these" and insert -those--.

3401212.) M15 LQIJXLED HI 2% 1971 Attest- EIMM. FlewherJr. mm squuyma,JR

Attesting Officer 0011115510216! of Patents

